Fabric material

ABSTRACT

Fabric material has nonconductive core yarn, and conductive sheath yarn arranged in a spiral pattern around the core yarn. The sheath yarn includes conductive first yarn, and second yarn. At least five strands of the first yarn are arranged close-packed together while being twisted around the second yarn.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2011-047724 filed on Mar. 4, 2011 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to fabric material provided with insulating core yarn, and conductive sheath yarn (wire arranged in a spiral pattern around the core yarn).

2. Description of Related Art

Japanese Patent Application Publication No. 7-161456 (7-161456) describes an example of such fabric material. This fabric material has a heating wire (core yarn and conductive sheath yarn). The core yarn is wire made of polyester and cotton, and the sheath yarn is wire made from metal wire such as stainless steel. With the related art, the heating wire is formed by arranging one strand of the sheath yarn in a helix pattern around the core yarn. Next, the fabric material is formed by weaving the heating yarn together with another wire (i.e., an insulating wire). This type of fabric material can be used for a cover of a vehicle seat, for example. Also, the cover will function as a heating member when current is applied to the heating wire.

With the structure described above, the cover may be pulled out of shape and folded over due to an occupant getting into and out of a vehicle or the like. At this time, a heating wire may be repeatedly flexed such that stress concentrates at the sheath yarn (a single metal wire), resulting in the wire breaking.

SUMMARY OF THE INVENTION

The invention inhibits, to the greatest extent possible, the conductive sheath yarn from breaking as a result of being flexed.

A first aspect of the invention relates to fabric material that has insulating core yarn, and conductive sheath yarn arranged in a spiral pattern around the core yarn, and that is able to be used for a cover of a vehicle seat, for example. The fabric material of this aspect of the invention functions as a heating member by current being applied to the sheath yarn. Accordingly, it is desirable to inhibit, to the greatest extent possible, the sheath yarn from breaking as a result of being flexed. Therefore, with the fabric material according to this aspect, the sheath yarn includes conductive first yarn, and second yarn. At least five strands of the first yarn are arranged close-packed together while being twisted around the second yarn. According to this structure, the expansion and contraction difference between the inner and outer diameters during flexing is reduced, and flexing deformation is reduced by the twist structure.

In the fabric material described above, the second yarn may be wire that has an initial tensile resistance of at least 4.9 GPa, and that has a higher degree of elongation than the first yarn (i.e., the second yarn may be a highly elastic wire). According to this structure, the flex resistance and tensile strength of the sheath yarn are able to be improved.

According to the aspect described above, the conductive sheath yarn is inhibited, to the greatest extent possible, from breaking as a result of being flexed.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a perspective view of a vehicle seat;

FIG. 2 is a front view of a portion of fabric material;

FIG. 3A is a side view of a first wire;

FIG. 3B is a side view of another example of a first wire;

FIG. 4 is a side view of yet another example of a first wire;

FIG. 5A is a sectional view of sheath yarn;

FIG. 5B is a sectional view of sheath yarn according to a first modified example;

FIG. 5C is a sectional view of sheath yarn according to a second modified example;

FIG. 5D is a sectional view of sheath yarn according to a third modified example;

FIG. 6 is a front view of a portion of a connecting member and fabric material;

FIG. 7 is another front view of a portion of the connecting member and fabric material;

FIG. 8 is a sectional view of a portion of the connecting member and fabric material;

FIG. 9A is a sectional view schematically showing sheath yarn of a reference example;

FIG. 9B is another sectional view schematically showing the sheath yarn;

FIG. 9C is still another sectional view schematically showing the sheath yarn; and

FIG. 10 is a schematic diagram of a test circuit.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, example embodiments of the invention will be described with reference to FIGS. 1 to 10. In FIG. 1, reference character F denotes a forward direction with respect to the members, reference character B denotes a backward or rearward direction with respect to the members, reference character UP denotes an upward direction with respect to the members, and reference character DW denotes a downward direction with respect to the members. In the schematic diagrams of sheath yarn in FIGS. 9A and 9B, the sheath yarn is shown aligned, not twisted, to facilitate understanding. A vehicle seat 2 in FIG. 1 has a seat cushion 4, a seat back 6, and a headrest 8. Each of these members has a cushion (4P, 6P; and 8P) that forms the outer shape of the seat, and a cover (4S, 6S, and 8S) that covers the cushion. Polyurethane foam (having a density of 10 kg/m³ to 60 kg/m³) may be used for a typical cushion, for example.

In this example embodiment, fabric material 10 serves as a heating member while being used for the cover described above (see FIGS. 1 and 2). The fabric material 10 has a first wire 20 f (i.e., core yarn 22, and sheath yarn 24) as constituent yarn (see FIGS. 2 and 3). With the first wire 20 f, the conductive sheath yarn 24 is arranged in a spiral pattern around the core yarn 22. With this type of structure, it is preferable to inhibit, to the greatest extent possible, the sheath yarn 24 from breaking as a result of being flexed. Therefore, in this example embodiment, the structure described below is employed to inhibit, to the greatest extent possible, the sheath yarn 24 from breaking. The structures will now be described in detail.

The fabric material 10 has a plurality of constituent yarns (i.e., the first wire 20 f and a second wire 20 s) and a connecting member 12 (see FIGS. 2 and 6). The connecting member 12 enables the fabric material 10 to function as a heating member by applying current to the fabric material 10 (i.e., the first wire 20 f) and heating it up. The fabric material 10 may be woven fabric, knit fabric, or nonwoven fabric, but in this example embodiment, woven fabric is manufactured as the fabric material 10. The woven fabric of the fabric material 10 may be woven fabric of any structure such as plain weave fabric, twill weave fabric, or sateen weave fabric, for example.

The first wire 20 f is a conductive wire capable of conducting electricity, and includes the insulating core yarn 22 and the conductive sheath yarn 24 (i.e., first yarn 41 and second yarn 42) (see FIGS. 3 to 5). In this example embodiment, the required value differs depending on the use, but a first wire 20 f having a resistance value of 0.1 to 47 Ω/cm measured in compliance with JIS C 2525 is preferably used.

The core yarn 22 is wire (insulating wire) with a specific resistance that typically exceeds 10⁸Ω×cm. The material of the core yarn 22 is not particularly limited, but a possible example is yarn made using natural fiber (a natural fiber of a plant system or an animal system, or a regenerated fiber such as rayon), or synthetic fiber (a synthetic fiber such as polyamide or polyester, or a semi-synthetic fiber such as acetate). Only one of these types of fiber or yarn may be used, or two or more types may be used together, as the core yarn 22.

The sheath yarn 24 is wire that is arranged in a spiral pattern around the core yarn 22, and includes the first yarn 41 and the second yarn 42 that will be described later. The sheath yarn 24 may be a single covering or a double covering, and the twisting direction of the sheath yarn 24 may be either an S-twist or a Z-twist (see FIGS. 3A and 3B). The number of twists of the sheath yarn 24 with respect to the core yarn 22 is set appropriately according to the thickness (i.e., fineness) and the like of the core yarn 22 and the sheath yarn 24. For example, with a single covering, the first wire 20 f is able to be given the desired durability by setting the number of twists of the sheath yarn 24 to 20 to 2000 T/m. If the number of twists of the sheath yarn 24 is less than 20 T/m, the desired durability of the first wire 20 f tends not to be able to be obtained. Here, when the sheath yarn 24 is a single covering, a third yarn 43 (i.e., another wire that is different from the sheath yarn 24) can also be twisted in the opposite direction of the sheath yarn 24 in order to prevent the sheath yarn 24 from untwisting (see FIG. 4). For example, if the sheath yarn 24 is a Z-twist, the third yarn 43 will be an S-twist. The material of the third yarn 43 is not particularly limited. For example, the same material as that of the second wire 20 s that will be described later and the core yarn 22 may be used.

The first yarn 41 is yarn that is always arranged on the outer periphery of the sheath yarn 24, and the second yarn 42 is always arranged at the center of the sheath yarn 24, as shown in FIGS. 5A to 5D. In this example embodiment, wire having a specific resistance (i.e., a volume resistivity) of 10⁰ to 10⁻¹²Ω×cm measured in compliance with JIS C 2525 may be used as the first yarn 41 and the second yarn 42. Metal wire is one possible example of the first yarn 41 and the second yarn 42 (see FIG. 5A). Examples of the metal wire may be wire of gold, silver, copper, brass, platinum, iron, steel, zinc, tin, nickel, stainless steel, aluminum, or tungsten or the like. The metal wire used in the first yarn 41 and the second yarn 42 typically has a low elastic elongation range of approximately 0.3 to 0.5%. Elongation greater than this is in a plastic deformation region and will result in fatigue failure. Of these, stainless steel metal wire is preferably used because it has excellent corrosion resistance and strength. Here, the stainless steel (i.e., the type thereof) is not particularly limited. Possible examples include SUS304, SUS316, and SUS316L. SUS304 has wide applicability, and SUS316 and SUS316L have good corrosion resistance because they include molybdenum.

Also, a possible example of the second yarn 42 is wire with high elasticity and a higher degree of elongation than the first yarn 41 (such as highly elastic wire) (see FIG. 5B). Having the second yarn 42 be wire with high elasticity and a higher degree of elongation than the first yarn 41 means that the second yarn 42 will bear the tensile force applied to the sheath yarn 24, so the flex resistance and tensile strength of the sheath yarn 24 is able to be improved. Highly elastic yarn is wire with an initial tensile resistance of equal to or greater than 4.9 GPa (and typically 4.9 GPa to 600 GPa), and more preferably, wire with an initial tensile resistance of 54 GPa to 280 GPa. The initial tensile resistance can be measured based on JIS L 1013 8.10.

Yarn such as industrial polyester yarn or high-strength polyethylene yarn may be used as the highly elastic yarn (i.e., the material thereof), but material with a variety of excellent characteristics is preferably used. Examples of material with a variety of excellent characteristics (i.e., material that is very strong, has a high melting point, or is flame retardant) include a para-type aramid fiber, a meta-type aramid fiber, a polyarylate fiber, a poly-para-phenylene benzobis oxazole fiber, a polyphenylene sulfide fiber, a polyether ether ketone fiber, a polyimide fiber, and a PAN-based carbon fiber. Examples of a para-type aramid fiber (having an initial tensile resistance of 54 GPa to 199 GPa) include Kevlar (Trademark) by DuPont and Technola (Trademark) by Teijin. An example of a polyarylate fiber (having an initial tensile resistance of 74 GPa to 104 GPa) is Vectran (Trademark) by Kuraray. Also, an example of a poly-para-phenylene benzobis oxazole fiber (having an initial tensile resistance of 180. GPa to 280 GPa) is Zylon (Trademark) by Toyobo.

In this example embodiment, five or more (typically five to ten) strands of the first yarn 41 are arranged close-packed together while being twisted around the second yarn 42, thereby forming the sheath yarn 24 having a desired diameter (see FIGS. 5A to 5D. Here, the phrase “close-packed together” refers to the maximum number of strands that are arranged together when the strands of the first yarn 41 are closely arranged circumscribing the second yarn 42. For example, when the diameters of the first yarn 41 and the second yarn 42 are the same, the number of strands of the first yarn 41 is six. The diameter of the sheath yarn 24 is not particularly limited, but is preferably a diameter of 30 to 200 μm, for example. If the diameter of the sheath yarn 24 exceeds 200 μm, the sheath yarn 24 becomes rigid and may feel like a foreign body to an occupant. Here, the diameter of the metal wire is preferably set to 10 to 50 μm (a relatively small diameter). Also, having both the first yarn 41 and the second yarn 42 be metal wire enables a sheath yarn 24 with a diameter of 30 to 150 μm to be made. Also, the diameter of the highly elastic yarn is preferably set to 20 to 100 μm. Having the first yarn 41 be metal wire and the second yarn 42 be highly elastic yarn enables a sheath yarn 24 with a diameter of 40 to 150 μm to be made.

The sheath yarn 24 (particularly the first yarn 41) is preferably more heat resistant than the second wire 20 s (that will be described later) and the core yarn 22. In other words, it is preferable that the temperature at which the sheath yarn 24 will melt from being heated, or the temperature at which the sheath yarn 24 will start to burn in a case in which the sheath yarn 24 does not melt, be higher than that of the second wire 20 s and the core yarn 22. That is, it is preferable that the sheath yarn 24 be yarn that has a higher melting point than the second wire 20 s and the core yarn 22, or that the sheath yarn 24 not burn as easily as the second wire 20 s and the core yarn 22. The limiting oxygen index (LOI) measured in compliance with JIS K 7201 and JIS L 1091 (1999) 8.5 E−2 (oxygen index method test) may be used as the combustibility index. Sheath yarn 24 with an LOI of 26 or greater is preferable. The metal wire described above typically has a higher melting point than the natural fiber or synthetic fiber used for the second wire 20 s, and the LOI is normally 26 or greater. For example, the LOT of stainless steel fiber is 49.6.

The second wire 20 s is wire with a specific resistance that typically exceeds 10⁸Ω×cm (see FIGS. 2 and 6). The material of the second wire 20 s is not particularly limited, but a possible example is yarn made using natural fiber or synthetic fiber (see FIG. 2). Only one of these types of fiber or yarn may be used, or two or more types may be used together, as the second wire 20 s.

When the second wire 20 s is wire in which the temperature at which it melts from being heated, or, if it does not melt, the temperature at which it burns (i.e., the temperature at which it starts to burn), is lower than that of the sheath yarn 24 (particularly the first yarn 41), the LOI is preferably less than 26. The LOI of natural fiber is often less than 26. For example, the LOI of cotton is 18 to 20 and the LOI of wool is 24 to 25. Moreover, synthetic fiber often has a lower melting point than the sheath yarn 24 (i.e., the first yarn 41), and the combustibility is often higher than that of the sheath yarn 24 (i.e., the first yarn 41). For example, the LOI of polyester fiber is 18 to 20, and the LOI of nylon fiber is 20 to 22.

A single (i.e., one) strand of the first wire 20 f may be woven in between the second wires 20 s, or a plurality of strands (2 to 10 strands, more particularly 2 to 5 strands) may be woven in consecutively (see FIGS. 2 and 6). In FIGS. 2 and 6, for the sake of convenience, portions of the fabric material 10 that are formed by the second wire 20 s are denoted by reference character 20 s. Here, an interval W1 between the first wires 20 f that are in between the second wires 20 s is not particularly limited, but the interval is preferably 2 to 100 mm, and more preferably 5 to 50 mm (see FIG. 6). If the interval W1 is narrow (for example, if it is set to less than 2 mm), heating is able to be even. However, the current to each first wire 20 f will be less so the temperature will drop, or the power consumption will increase if the voltage is increased to raise the temperature. Also, if the interval W1 is wide (for example, if it is set greater than 100 mm), the current to each first wire 20 f will be greater so the temperature will rise, or power consumption can be suppressed by reducing the voltage. However, the temperature would tend to be uneven because the interval W1 is wide.

When the fabric material 10 is used for the cover (i.e., heating member), the entire surface of the vehicle seat 2 (i.e., the seat cushion 4 and the seat back 6) can be heated more evenly by weaving the first wires 20 f in at substantially equal intervals (see FIG. 1). Also, if there is a desire to warm a specific area of a seated person (such as the thighs, shoulders, or back, for example) more thoroughly, the first wires 20 f may be arranged relatively close together at the area corresponding to the fabric material 10 (i.e., the heating member), and relatively farther apart at other areas.

The method for manufacturing the cover involves a cutout process and a connecting process. In the cutout process, a piece of woven fabric of a desired shape is cut out from the raw fabric of the fabric material 10. The method by which the piece of woven fabric is cut out from the raw fabric is not particularly limited. For example, it may be cut out with a cutter, or cut out by emitting a laser such as a carbon dioxide laser, a YAG laser, or an excimer laser.

In the connecting process, the connecting members 12 are connected to both side end portions of the fabric material 10 (i.e., the cover member), and the first wires 20 f are connected to an ECU, not shown (see FIG. 6). For example, both end portions of each of a plurality of first wires 20 f are electrically connected to the connecting members 12 for connecting to the ECU. In the connecting process, both end portions of the first wires 20 f are connected to conductors of the connecting members 12, and a connecting terminal on the end portion in the length direction of each connecting member 12 is connected to the ECU. As a result, power is able to be supplied from a power supply in response to a signal from the ECU, such that current passes through the first wires 20 f.

The structure of the connecting member 12 is not particularly limited. One example is a connecting member 12 of a strip of base material made of woven fabric or the like, that is plated on at least the surface to which the end portion of each first wire 20 f is attached (see FIGS. 6 to 8). With this connecting member 12, the end portions of the first wires 20 f and a plated layer 12 a (one example of a conductor) are connected and fixed together by overcasting or the like (suture line SEW1). Then, one of the side end portions of the strip of base material is attached by being sewn to a side end portion of the fabric material 10 (suture line SEW2). The connecting member 12 is preferably flexible to facilitate the work of attaching it to the fabric material 10 (i.e., the cover) and to make it more easily able to deform under a load when an occupant sits in a seat such as a vehicle seat.

Here, the insulating second wire 20 s and core yarn 22 and the like are weaved in near both end portions of the first wires 20 f. These members (i.e., the insulating material) must be removed before attaching the connecting member 12. The insulating material has a lower melting point than the first wires 20 f, or start to burn at a lower temperature than the first wires 20 f, so the insulating material can be removed by being melted or burned off by heating both side end portions of the piece of woven fabric. The heating method is not particularly limited. Some examples include a method according to exothermal heating that involves contacting the side end portions of the piece of woven fabric with a heating member or the like, and a method that involves emitting a laser such as a carbon dioxide laser, a YAG laser, or an excimer laser. The method of emitting a laser is preferable.

If the method of emitting a laser is used, the strength and output of the laser can be easily adjusted to the level needed to melt or burn off the insulating material, by the material of the insulating material and the like, thus making it possible to efficiently remove the insulating material. Moreover, the laser may be emitted from either surface of the fabric material 10. Emitting the laser with the focal point offset with respect to the surface of the fabric material 10 temporarily enables a wider area to be worked. Also, the insulating material is able to be removed in strips by emitting the laser back and forth on the fabric material 10. Further, spraying an inert gas, such as nitrogen gas or helium gas, while emitting the laser makes it possible to prevent, or at least reduce, oxidation degradation of the first wire 20 f (i.e., the sheath yarn 24) that occurs from heating.

The fabric material 10 is used for the cover of the seat cushion 4, for example (see FIGS. 1 and 2). At this time, the position of the connecting member 12 in the width direction of the seat cushion 4 is not particularly limited, but if the connecting member 12 is at a portion of the seat cushion 4 that is contacted by the buttocks or the thighs or the like, it may feel hard and uncomfortable. Also, when the connecting member 12 is used in the seat back 6, if it is at a portion of the seat back 6 that is contacted by the back or shoulders or the like, it may feel hard and uncomfortable. Therefore, the connecting member 12 is preferably arranged in a position to the outside of a stitching portion where the connecting member 12 is stitched together with another member such as side member that is adjacent to the cover. In this way, discomfort to a seated occupant will be minimized and durability can be improved.

With this kind of seat structure, the cover may be pulled out of shape and folded over due to an occupant getting into and out of the vehicle, as described above (see FIG. 1). At this time, problems occur such as stress concentrating at the sheath yarn 24 due to the first wires 20 f flexing and being pulled. At this time, with the sheath yarn 24 in this example embodiment, five or more strands of the first yarn 41 are arranged close-packed together while being twisted around the second yarn 42 (see FIGS. 5A to 5D). Using the five or more strands of the first yarn 41 (wire with a relatively small diameter) enables the difference in elongation of each strand of the first yarn 41 with respect to the center line (see the broken line CL in FIG. 9A) when the first wire 20 f is flexed (i.e., curved) to be less than it is when there is one strand of the same diameter (see FIGS. 9A and 9B). Also, twisting each of the strands of the first yarn 41 makes it possible to reduce deformation of the sheath yarn 24 when the first wire 20 f is flexed. That is, when the twist is thought of as being coil-shaped, flexion deformity of the sheath yarn 24 is able to be reduced by the deformation of the coil shape (see FIG. 9C). Also, the reason for closely packing the strands of the first yarn 41 is to stabilize the twist structure. If the twist structure is not stabilized and the twisting is loose, the effect of the twist structure of that portion, i.e., the effect of reducing flexion deformity, is lost, and as a result, that portion becomes a weak portion, which is undesirable. The second yarn 42 is always arranged at the center of the sheath yarn 24 and is shorter than the first yarn 41 such that when the sheath yarn 24 is elongated, tension is easily placed on the second yarn 42. At this time, the second yarn 42 is wire with a high initial tensile resistance and a higher degree of elongation than that of the first yarn 41, so the second yarn 42 will bear the tensile force applied to the sheath yarn 24, thereby protecting the conductive first yarn 41, and thus improving the flex resistance of the sheath yarn 24. Here, the degree of elongation is increased in order to increase the elastic elongation range of the second yarn 42 so that it is greater than the elastic elongation range of the first yarn 41, as well as to prevent the second yarn 42 that is placed under tension from breaking due to fatigue. Also, the reason for making the second yarn 42 highly elastic is because tension will be placed on it. In the example embodiment described above, the foregoing structure reduces the stress on each of the strands of the first yarn 41. Therefore, this example embodiment makes it possible to inhibit, to the greatest extent possible, the conductive sheath yarn 24 from breaking as a result of being flexed.

Hereinafter, the example embodiment will be described based on examples, but the invention is not limited to these examples.

In Example 1, polyethylene terephthalate (PET) memory-twisted textured yarn (330 dtex, 96 filament) was used as the core yarn. Also, six strands of the first yarn of SUS316 (φ20 μm, a degree of elongation of 1.5%, and an elastic elongation range of 0.5%) and one strand of the second yarn of SUS316 (φ20 μm, a degree of elongation of 1.5%, and an elastic elongation range of 0.5%) (for a total of seven strands) were used as the sheath yarn. The sheath yarn (with a diameter of 60 μm) was prepared by arranging these six strands of the first yarn close-packed together while being twisted around the second yarn, with the number of twists of the six strands of the first yarn set at 10.00 T/m. Then, the core yarn was double-covered with S- and Z-twists by this sheath yarn, thus creating the first wire of Example 1.

Also, a PET memory-twisted textured yarn (167 dtex, 48 filaments) was used as the second wire. After warping the warp yarn (i.e., the second wire), the first wire was punched in in cycles of one strand for every 90 strands of weft yarn, while punching in the second wire (i.e., the weft yarn) using a Jacquard knitting machine. Next, the fabric material underwent a well-known finishing process (brushing and shearing), and then a backing agent was adhered to the back side and dried, thus creating the fabric material of Example 1. The main components of the backing agent used were an acrylic-type polymer, made by copolymerizing butyl acrylate and acrylonitrile, and a flame retardant. Also, the amount of backing agent applied was 45 g/m², and the drying temperature was 150° C. for 1 minute. The finished density of the fabric was a warp of 220 and a weft of 110 strands per 2.54 cm. Also, the interval dimension (W1) of the conductive wires was 20 mm.

In Example 2, eight strands of the first yarn in Example 1 and one strand of the second yarn of polyarylate fiber (φ36 μm, a degree of elongation of 3%, and an elastic elongation range of 2%) with an initial tensile resistance of 77 GPa (for a total of nine strands) were used as the sheath yarn. Next, sheath yarn (having a diameter of 76 μm) was prepared by arranging these eight strands of the first yarn close-packed together while being twisted around the second yarn, with the number of twists of the eight strands of the first yarn set at 1000 T/m. Then fabric material of Example 2 was prepared by the same method used in Example 1.

In Comparative example 1, one strand of the first yarn of SUS316 (φ60 μm) was used as the sheath yarn. Then fabric material of Comparative example 1 was prepared by the same method used in Example 1. The core yarn is double covered by the sheath yarn, so there are two strands of the sheath yarn in the first wire.

In Comparative example 2, four strands (with the number of twists being 1000 T/m) of the first yarn in Example 1 were used as the sheath yarn. Then fabric material of Comparative example 2 was prepared by the same method used in Example 1.

In Comparative example 3, six strands of the first yarn of Example 1 and one strand of the second yarn of Example 1 were used as the sheath yarn. Next, the first yarn and the second yarn were aligned (without being twisted), thus creating the sheath yarn. Then fabric material of Comparative example 3 was prepared by the same method used in Example 1.

A flexibility test was then conducted using each example and each comparative example. A sample 80 mm across (i.e., in the direction in which the first wire is woven in) and 25 mm tall was cut out of the fabric material of each example and each comparative example. Then the sample was repeatedly flexed 120° on one side from a straight state with a curvature radius of 1 mm, and the breaking number of the first wire was checked. In this test, the breaking number of the first wire was checked using the circuit shown in FIG. 10. Current was passed through the first wire, and while monitoring the voltage, the flexing portion was observed when the voltage was changed, and the number of times at which it was confirmed that one bunch broke was set as the breaking number.

The results will be described below. With Comparative example 1, the first wire broke after being flexed approximately 2,000 times. Also, with Comparative example 2, the first wire broke after being flexed approximately 7,500 times. With Comparative example 3, the first wire broke after being flexed approximately 5,000 times. In contrast, with Example 1, the first wire broke after being flexed approximately 30,000 times. Also, with Example 2, the first wire broke after being flexed approximately 50,000 times. From this, it is evident that with the fabric material in Examples 1 and 2, the conductive sheath yarn is able to be inhibited, to the greatest extent possible, from breaking as a result of being repeatedly flexed. As a result, it is presumed that arranging the five or more strands of the first yarn close-packed together while twisting them around the second yarn yields a stable twist structure, and the twist structure reduces deformation from flexing. Also, by making the second yarn a yarn with a highly elastic and a high degree of elongation, it is presumed that it will bear the tension so the bending durability will improve. In a typical cushion durability evaluation, 25,000 or more individual durability tests is passing, so the fabric material of Examples 1 and 2 is understood to be significant.

The fabric material of this example embodiment is not limited to the example embodiment described above. That is, other various example embodiments are also possible. For example, (1) the fabric material of this example embodiment may be used for the cover (e.g., 4S, 6S, and 8S) of various structures of the vehicle seat 2, such as a center top portion, a side top portion, a stile portion, or a back lining portion. Also, the fabric material may be used for the covers of various types of seats, such as a household seat, in addition to the cover of a vehicle seat. (2) Also, in this example embodiment, the fabric material 10 is described as functioning as a special heating member. The fabric material 10 may also be used as an antenna or an electrode of a capacitance sensor. In this case, a single connecting member may be attached to only one side of the fabric material 10. (3) Also, in this example embodiment, an example is described in which the cover itself is formed by fabric material, but the structure of the cover is not limited to this. For example, the fabric material 10 may also be attached to the back surface of front material (i.e., the cover itself). At this time, padding (such as polyurethane lamination) may also be arranged between the front material and the fabric material, or on the back surface of the fabric material. 

1. Fabric material comprising: insulating core yarn; and conductive sheath yarn arranged in a spiral pattern around the core yarn, wherein the sheath yarn has at least five strands of conductive first yarn, and second yarn, and the strands of the first yarn are arranged close-packed together while being twisted around the second yarn.
 2. The fabric material according to claim 1, wherein the second yarn is wire that has an initial tensile resistance of at least 4.9 GPa, and that has a higher degree of elongation than the first yarn.
 3. The fabric material according to claim 1, wherein a number of twists of the first yarn set to at least 1000 T/m. 